PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 755 



These charges, to the number of thirty or more, are placed under 

 a hydraulic press, and a pressure is applied at first from fifteen to 

 twenty atmospheres to the square inch, gradually increasing to 

 one hundred and twenty to two hundred atmospheres. 



The pressing surface is generally twenty-four inches, and each 

 press cloth is charged with sixteen jiounds of pulp. The pressure 

 is regularly increased for from eight to fifteen minutes, remains 

 thus for some five minutes, and is then released : the juice ex- 

 pressed during this operation ranges from eighty to eighty-four 

 per cent, of the weight of the beets. 



Beside silk, wool, horsehair and hemp are used for press cloths. 

 Frequent washing of these is necessary, ammonia commonly being 

 added to the water to neutralize acidity and dissolve slime ; soda 

 and lime were formerly used for this purpose, but it was found 

 that these soon weakened the fibre of the cloth. The pressed 

 cakes are used as cattle-feed. 



Another method of separating the saccharine juice from the 

 pulp, first introduced by Schottler, is by placing it in a metallic 

 cylinder finely perforated, and caused to revolve at the rate of one 

 thousand revolutions per minute. The centrifugal force causes 

 the juice to be expressed, but a great amount of fine pulp is driven 

 out with it through the meshes, causing trouble in the subsequent 

 operation of defecation. By this method, also, an inmiense amount 

 of froth is produced, which has to be run separately into a vat, 

 and condensed with steam. A charo^e for a centrifuije is two hun- 

 dred pounds, and this is exhausted in fifteen minutes, or thirty 

 charges can be made easily in a day. Among other methods 

 which have been used may be mentioned ordinary rollers, pressure 

 with compressed air or gases ; these have been tried, though, 

 with but little success. The method of maceration lately came 

 into use, recommends itself for its completeness and simplicity ; 

 'also in that it does away with expensive pumps and presses. In 

 the cells of beet pulp, in contact with water for some time, an 

 endosmotic process is carried on, the water entering the cells and 

 giving out the saccharine juice, until the liquid within and wdth- 

 out possesses an equal density. If, then, one hundred pounds of 

 beets, reduced to pulp containing ninet3'--six pounds of juice, are 

 mixed with an equal weight of water, endosmosis w^ill produce a 

 juice of half the original strength, but double the quantity. If 

 this be withdrawn, and the same proportion of fresh water be 

 again added, the juice contained in the cell of half the original 



